1. Field of the Invention
The present invention relates to a process cartridge, a method for assembling a process cartridge and an image forming apparatus containing the cartridge. The image forming apparatus may be, for example, a laser beam printer, an electrophotographic copying machine, a facsimile machine, a word processor or the like.
2. Related Background Art
In an image forming apparatus such as a printers, a latent image is formed by selectively exposing an image bearing member which has been uniformly charged. The latent image is then visualized with toner as a toner image, which is, in turn transferred onto a recording sheet, thereby recording an image on the recording sheet. In such apparatuses, whenever the toner is consumed or used up, new toner must be replenished. However, the toner replenishing operation is not only troublesome, but also often causes the contamination of surroundings. Further, the maintenance of various elements of the apparatus must be performed periodically.
To this end, a so-called process cartridge can be facilitated has been proposed and put into practical use (for example, as disclosed in U.S. Pat. Nos. 3,985,436, 4,500,195, 4,540,268 and 4,627,701) wherein a photosensitive drum, a charger, a developing device, a cleaning device and the like are integrally contained in a cartridge housing which can be removably mounted to an image forming apparatus, and whereby the replenishment of toner or the exchange of parts, the service lives of which have expired, can be permitted and maintenance can be facilitated.
When such a process cartridge is mounted to an image forming apparatus, an electric contact of the image forming apparatus is slidingly contacted with an electric contact of the process cartridge to electrically earth the image bearing member. Due to such sliding contact between the electric contacts, a load is generated in a cartridge inserting direction.
On the other hand, in a laser beam printer using a process cartridge, in order to prevent the laser light from leaking out of the apparatus to other than the image forming operation, an openable laser light path blocking means (laser shutter) is provided in a laser light path. In order to open and close the laser shutter, a projection for opening and closing the laser shutter is provided on the process cartridge so that, when the process cartridge is inserted into the printer, the projection is abutted against a portion of the blocking means to open the laser shutter. When the projection is abutted against the blocking means, a load is also generated in the cartridge inserting direction.
Further, a protection cover for covering an exposed portion of an image bearing member to prevent the deterioration of the image bearing member when a process cartridge is dismounted from an image forming apparatus has already been put into practical use. The opening of the protection cover is effected by abutting the protection cover against a portion of the image forming apparatus when the process cartridge is inserted into the image forming apparatus. When the protection cover is opened during the insertion of the process cartridge, a load is also generated in the cartridge inserting direction.
As mentioned above, when the process cartridge is inserted into the image forming apparatus, various loads are generated in the cartridge inserting direction. Thus, it is possible for any play to occur during the cartridge mounting and dismounting operation, thereby worsening the accuracy of the cartridge loading operation.